Player with Gazebo: libprotobuf error messages.

I'm trying to control Pioneer2dx with Player, and visualize in Gazebo.
I'm using Gazebo 1.9.1, Player 3.0.2.

I made the model of Pioneer2dx with Hokuyo laser on it in the Gazebo world.
When I the Gazebo world file, and execute 'position2d.cfg', which is one of the example file.
And used simple client 'playerv'.
Here is my 'position2d.cfg' file.

driver

(

name "gazebo"

provides ["simulation:0"]

plugin "libgazebo_player"

# The name of a runnign Gazebo world, specified in a .world file

world_name "default"

)

driver

(

name "gazebo"

provides ["position2d:0"]

# This name must match the name of a model in the "default" world

model_name "pioneer2dx"

)

Controlling the pioneer with gui by 'command' menu was fine. The problem is,
When I subscribe position2d:0, the terminal window which executed 'position2d.cfg' emits error messages repeatedly. The error message is following.